Improvement in the manufacture of paints



UNITED STATES PATENT @rrrcn...

G. F. DE DOUHET, OF PARIS, FRANCE.

IMPROVEMENT IN THE MANUFACTURE OF PAINTS.

Specification forming part of Letters Patent No. ,356, dated September9, 1851.

To all whom it may concern Be it known that I, GUILLAUME FERDI- NAND DEDOUHET, of the city of Paris, in France, have invented a new and usefulImprovement in the Manufacture of Chemical Oolorin g Compounds; and I dohereby declare that the following is a full, clear, and exactdescription of the same and of the manner in which it is to be appliedin the arts.

The deoxidation or loss of oxygen which is undergone by certainbodiesimparts to them new properties useful tothe arts and industry. It isthis deoxidation and the applications resulting therefrom that form theobject of this invention.

The bodies which it is here intended to deoxidize are all sulphatessoluble in water, metallic or alkaline, and certain insolublesulphates-such as those of barytes, of strontian, and of lime. Thedeoxidatio'n of the first is made by the humid method, and t-hat'of thesecond by the dry method. I deoxidize sulphates by the humid method byplacing these sulphates dissolved in water in contact with sulphurets,likewise dissolved in water, and which in this state have a strongtendency to become again sulphates by receiving oxygen from the bodieswhich are being deoxidized.

In order that the operation may give products free from impurity, one ofthe two substances which combine must generally form an insolubleprecipitate from the moment the mixture is made, so that the otherremains transformed and dissolved in the liquid; but sometimes it ismore useful for obtaining certain products to cause the formation of adouble precipitate on the part of the two substances, as I willhereinafter explain.

In the system of deoxidation the deoxidizing body is a solublesulphuret, the body to be deoxidized or deoxidated is any sulphatelikewise soluble, and the precipitates are obtained pure or mixed,according as one or both of the two bodies producing this doubledecomposition have the property of bein g precipitated from the liquidswhich kept them dissolved before they were placed in contact. The wateryor aqueous solutions of the sulphurets of barium, strontium, andcalcium, otherwise called the hydrosulphurets of baryta, of strontia,and of lime, are powerful agents for deoxidizing all soluble sulphates.,I place in the first rank for this object sulphuret of barium when twosolutions, one of sulphuret of barium and theotherot'anysulphatesulphate of soda, for instance'are mixed. Thesulphuret of barium, receiving oxygen from the sulphate of soda,becomesagain sulphate ofbaryta, and is precipitated, while the deoxidizedsulphate of soda is transformed into hydrosulphuret and remainsdissolved in the liquid. The deoxidation of the sulphate is complete ifthe two materials for the double decomposition be mixed proportionallytotheir respective equivalents, while it is partial if the sulphuretedsolution is employed in less quantity than the equivalent of thesulphate. The same principles are applicable to the sulphate of potashand of ammonia; but they are modified as to the metallic sulphates ofzinc, of copper, and of iron. Thus the sulphurets proceeding from thedeoxidation of these different sulphates are themselves insoluble inwater, and hence it is easy to conceive that they tend to precipitate atthe moment of their formation but as it is the same with the deoxidizingbody-the sulphuret of barium-it happens then that the twoingredients ofthe mixture are precipitated simultaneously, leaving the watersexhausted or free from either salt. However, it would not be thus if,instead of sulphurets of barium, of strontium, or of calcium, thesulphurets of sodium, potassium, or ammonia be employed as deoxidizingagents, for in regaining oxygen from the metallic sulphates thesesulphurets are again converted into sulphates; but they wouldnevertheless remain dissolved in the liquid, while the metallic bases,united with the sulphur, would precipitate alone and the solution. Thesecond,solids; they are the precipitates of sulphate of barytes,strontian, or lime, and the hydrated metallic sulphurcts, which areformed alone or mixed, according as the sulphate proceeding from thedeoxidizing bodies is soluble or insoluble. Now,all are applicable todifferent useful purposes inindustry,

whether they be used separately, simultaneously, or mixed together, as Iwill now explain. As to the deoxidation by the dry process, it appliesto insoluble sulphates of barytes, of strontian, and of lime,which,brought back to the state of sulphurets, are valuable agents, es-

pecially the sulphuret of barium, for the trans-- formations I havejustspoken of.

The deoxidation of these various bodies by their calcination withcarbonaceous substances in crucibles and furnaces has been long known. Iwill say nothing further on the process; but I must, however, make theremark that if it were intended to manufacture the sulphurets of barium,strontium, or calcium rapidly and in large quantities it would be betterto use the following method: calcine in any furnace, but better in areverberatory furnace, blocks or cakes composed in volume, forinstance,of half sulphate of baryta, in powder, and the other half ofcoal or charcoal, likewise in powder, and a sufficientquantity of fineclay mixed with water; or, still better, tar or asphalt to bind andspread over the whole. These blocks or bricks,dried till they haveacquired sufficient firmness, are placed in the furnace, and care istaken during their calcination, which ought to be intense and carried onat a red heat during several hours, to directupon them the greatestquantity of carbureted-hydrogen gas that can be obtained from thecombustion of the coal in the furnace. For this purpose the partcontaining the fire which throws the heat upon the sole on which thebricks are placed must have a sufficient depth to allow a thick layer ofcoals to be constantly kept ignited in it, so that a part of thehydrogen of the fuel may in this manner be projected upon theincandescent bricks of sulphate of baryta. The calcination being ended,these bricks or cakes, having become pulverizable, are washed in hotwater. A portion of the sulphate of baryta, deoxidized by the coal andhydrogen and converted into sulphuret of barium, dissolves in the waterused for washing, forming hydrosulphuret of baryta. This portion variesfrom a fourth to three-fourths of the weight of the raw sulphate used,according as the operation has been more or less effectively conducted,and whether a reverberatory furnace, which is the best, has beenemployed, or an ordinary pottery or lime kiln, which, though verypracticable, is less suitable. The surplus remains insoluble, in thewater in the form of an earthy and carbonaceous residue, and is anexcellent manure.

There is'still another method less generally used, but which in certaincases may be employed with advantage, and which is carried out in thefollowing manner: Place the sulphate of baryta, broken into bits, incylinders of cast-iron, open at both ends, communicating by one of thetwo ends with an apparatus evolving hydrogen, and at the other end bymeans of a curved tube with a tub full of water.

These cylinders are placed in a furnace in such a manner as to be easilybrought to a red heat, and during the operation it is necessary that thestream of hydrogen from the apparatus in communication should constantlycirculate on the sulphate, kept incandescent-at the same degree of heat.If these precautions be carefully observed, sulphuret of barium isobtained after several hours of calcination; and it the operation besuffieiently prolonged,'caustic baryta fit for the humid purposes forwhich it is used is obtained, for in this case the hydrogen, afterhaving deoxidized the sulphate, desulphurizes it. This last mode ofdeoxidation and of preparation of baryta is, moreover, applicable tomany other sulphates and oxides; but in certain cases, when the sulphateof baryta is siliceous, or when it is wished to accelerate itsdeoxitlatiomit is well to add to and to mix with the sulphate of barytain the cylinders a quantity of coal or of powdered charcoal inproportions varying according to circumstances.

Thei'ollowing is the specification of the products which the deoxidationof certain bodies by the humid way and by the dry way give rise to whenthey are made to react upon each other, some being in the state ofsulphates, the others in that of hydrosulphates, and the applicationthey are susceptible of in industry.

First. The sulphates of soda and of potash,

deoxidized by contact with the hydrosulphuret of baryta, as has beenexplained, arefit for the washing and whitening of wools or wovencloths, as well as the spun tissues of cotton and even of linen. Thesehydrosulphurets are employed according to the means used in washing,whether hot or cold, and sufficiently diluted to diminish their causticpower. They are,moreover, fit for the purposes to which the hydrates ofsoda and of potash are appliied by soap-makers, and form, when made intosoap, using oil and other ordinary materials, a good ordinary soaphaving soda or potash for its base. They may, moreover, serve for thefabrication of artificial soda or potash, for it is only requisite toextract the sulphur by exposing them very concentrated and halfcrystallized to the action of a stream of carbonic acid to obtain sodaor potash in the state of carbonate; but this manufacture can only beadvantageous if it is desirable to obtain a large quantity of artificialsulphate of barytes, which, as

has been before stated, forms the residue of this deoxidation. Thesesecondary or residuary products are among the economical results of myinvention.

Secondly. The hydrated metallic sulphurets or hydrosulphurets of zinc,copper, and iron, otherwise termed oxides of these different metals,mixed with sulphur, which, as aforesaid, are precipitate when theirdifferent sulphates are attacked by an alkaline hydrosulphuret whosesulphate is soluble in watersuch as soda and potashform white, black,greenish, and ocher colored precipitates, which, dried and calcined,become good colors to use in oil and varnish painting.

These samemetallic precipitates,prepared,on the contrary, by thedeoxidation of their sulphates by means of an alkaline hydrosulphuretwhose sulphate is insoluble-such as baryte's, strontian, and evenlime-form, according to the principles above specified, doubleprecipitates of hydrated sulphurets of zinc, copper, and iron, andsulphate of barytes, of strontian, or of lime, mixed together. Thesedouble precipitates, which form colors fit for oil or varnish paintingor for water-colors, are susceptible of important applications, and thusdeserve a special mention with respect to their fabrication and theiruse.

I mix together two aqueous solutions, the one of sulphate, either ofzinc, copper, or iron, the other of hydrosulphuret of baryta, both aboutequal in density. The solutions immediately yield up their respectivebases, which precipitate togetherin the form of an abundant pastecomposed of sulphate of baryta and of the metallic bases, united withsulphurin proportion to the equivalent of the two materials for thisdouble decomposition. The shade of color of this double precipitatedepends upon the various metals that have been used. The essential pointis that the double precipitation may take place to the thoroughexhaustion of the baryta and of the metal, zinc, copper, or ironcontained in the liquid, and we arrive at this result either by trial orby mixing the two ingredients of the combination proportionally to theirequivalents. This double precipitate, well washed, decanted, and dried,is afterward calcined at a red heat on the sole of a muffie-furnace orreverberatory furnace, and then thrown at an intense heat into coldwater, by which it gains that opacity which is in painting a valuablequality.

For painting in water-colors the process is more simple. I make useimmediately of the double precipitate the moment afterits formation andits subsequent washing, to apply it with water on the surface, to whichit adheres without any other preparation; and when this painting is dryit is sufficient to pass over ita single coat of varnish to preserve itfrom dampness and to render it durable. These various precipitates,treated as has been before said, constitute, that with the zinc base awhite color fit to replace cernse, (white lead,) that with the copper oriron base other fast colors of various shades.

In lieu of hydrosulphurets of baryta, strontian, or lime, prepared, asshown, by the dry method, and specially in place of the first, I

sometimes use as deoxidizing agents metallic sulphates, a solution ofpolysulphuret of lime prepared by the wet process by means of boilingtogether in water, sulphur, and lime. The double precipitate whichresults from its mixture with soluble metallic sulphates is notcomplete,for the lime has notthe same strength for precipitation asbaryta and strontian; but we may finish the operation by adding one ofthese hydrosulphurets to the liquid to be precipitated, and which hadresisted the action of the lime. The color obtained by this process,though inferior to that described above, may be substituted in certaincases.

The artificial sulphates of baryta or of strontian, which precipitatethemselves separately during the deoxidation above specified of thesulphates of soda or of potash, are susceptible of a new application.

It is known that the objection generally made to white oxide of zinc isthat it wants body and bubbles under the brush. To do away with theseobjections the artificial sulphate of baryta is excellent when employedin the following manner: Incorporate in the artificial sulphate ofbaryta, whenit isstillin the state of a paste, from fifty to seventy percent. of its weight of white zinc. The two substances are thoroughlymixed, then dried in small cakes which are calcined, and when redhotthrown into cold water, as has been shown above.

What I claim as my invention, and desire to secure by Letters Patent,is-- The manufacture by the processes, substantially as hereindescribed, of new colors fit for painting, whether with oil, varnish,spirits of turpentine, or water, bymeans of the deoxidation of .thesoluble metallic sulphates of zinc, copper, iron, and other metals, andby the precipitation of their bases either by alkaline hydrosulphuretswhose sulphates are solublesuch as those of soda, potash, and ammonia toobtain colorswith a single metallic base, or to obtain colors with adoublebase, partly metal and partly alkaline sulphate, by using thealkaline hydrosulphurets whose sulphates are insoluble-such as those ofbaryta, of strontian, and of lime, and even by the hydrated sulphuretsand polysulphurets of lime, prepared directly-substantially as hereinset forth.

G. F. DE DOUHET.

Witnesses:

J OHN BARTLY, O. GARDISSAL.

